The invention relates to a pad filled with a product to be extracted such as ground coffee and/or, optionally, a product to be dissolved such as a creamer for preparing a beverage, wherein the pad is designed in order that, in use, a liquid such as hot water can be fed under pressure to the pad for extracting and/or dissolving the product, the pad being provided with an optionally flexible bottom sheet manufactured from, for instance, filtering paper and an optionally flexible top sheet manufactured from, for instance, filtering paper, the top sheet and the bottom sheet being interconnected at their longitudinal edges so that that a covering with a circumferential sealing seam is formed with the product situated between the top sheet and the bottom sheet, the bottom sheet and the top sheet each forming a filter which is at least virtually impermeable to the product and which is at least permeable to water.
The invention also relates to an assembly of a pad and a holder in which the pad is included, wherein the pad is filled with a product to be extracted such as ground coffee and/or, optionally, a product to be dissolved such as a creamer, while the pad is provided with a bottom sheet manufactured from, for instance, filtering paper and a top sheet manufactured from, for instance, filtering paper, the top sheet and the bottom sheet being interconnected at their longitudinal edges in order that a covering with a circumferential sealing seam is formed, with the product situated between the top sheet and the bottom sheet, the bottom sheet and the top sheet each forming a filter which is at least virtually impermeable to the product and which is at least permeable to water, and wherein the holder is provided with a bottom and, optionally, an upstanding sidewall, while in the bottom at least one outflow opening is provided, the pad resting on the bottom while the assembly is designed in order that, in use, a liquid such as hot water can be fed under pressure to the assembly for extracting the pad.
Such a pad and such an assembly are known per se, for instance from the European patent application EP 0 904 717. The known assembly comprises a pad which is filled with a product to be extracted for obtaining an extract and affords possibilities for reducing the risk of bypass and increasing the coffee-making efficiency. Bypass is understood to mean that a liquid such as hot water is fed under pressure to the assembly, of which hot water then at least a part flows around the product in the pad to, thereupon, leave the holder of the assembly via the at least one outflow opening. Such bypass has as a result that, when the pad has for instance been filled with a product to be extracted, the extract which is for instance collected in a cup, is mixed with hot water. This gives the extract an undesired strength. It is not desired to make allowance for such bypass because it is not known beforehand what amount of water will flow to the cup without this being pressed through the bed of the product in the pad. Further, the water has the tendency to choose the path of least resistance, i.e., the water has the tendency to flow through specifically those places of the bed where the bed is relatively thin. This entails that the water flows relatively less through the thicker parts of the bed, resulting in the coffee-making efficiency not being optimal. For this phenomenon too, a solution is given in the European patent application EP 0 904 717.
An unfavourable property of certain embodiments of the known assembly is that the pressure in the holder can rise when the outflow opening becomes clogged. The pressure rises because the beverage cannot leave the holder while hot water is fed under pressure to a top side of the holder.